Thiophene dioxide derivatives. Part 5. 13C NMR spectroscopy and LIS in 1H spectra in determination of molecular geometry of 2,5-dihydrothiophene dioxide derivatives

The 13C NMR data and paramagnetic and benzene-induced chemical shifts in the proton spectra of sulfonene-3, its methyl derivatives and two analogous saturated compounds are discussed in terms of possible correlations with their molecular geometry. Bond angles distortion is assumed to be due to the nuclear repulsion of substituents in the planar ring skeleton. The shifts of γ-situated carbons reflect a sizeable steric effect of the S-O bond, while the inductive effect of heteroatoms is limited only to the α position. Steric interaction is diminished in saturated compounds, probably due to the relief of strain through the puckering of tetrahydrothiophene ring. (author)